Polymeric templating agent, stepped-pore lsx molecular sieve and green preparation method thereof

Abstract

The present application relates to the technical field of molecular sieve preparation, and particularly relates to a recyclable polymer template agent, a hierarchical-pore LSX molecular sieve and a green preparation method thereof. By using a polymer template agent with a special chemical structure, the synthesized LSX molecular sieve contains micropores and mesopores at the same time, forming a hierarchical-pore structure, and effectively solving the problems of low mass transfer efficiency and poor accessibility of active sites caused by the micropore structure of the conventional LSX molecular sieve. Meanwhile, the polymer template agent provided by the present application can be fully removed by centrifugation, and the synthesized LSX molecular sieve does not need to be calcined at high temperature, so that energy consumption is saved, and environmental pollution caused by high-temperature calcination is avoided, and the polymer template agent can be recycled and used for the preparation of the hierarchical-pore LSX molecular sieve. The hierarchical-pore LSX molecular sieve prepared by using the polymer template agent provided by the present application has a mesopore size of 20-50 nm, a specific surface area of 730-890 m 2 / g, and a pore volume of 0.55-0.65 cm 3 / g, which greatly improves the performance of the LSX molecular sieve.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of molecular sieve preparation, in particular to a recyclable polymer template agent, a hierarchical pore LSX molecular sieve and a green preparation method thereof. BACKGROUND

[0002] The conventional LSX type molecular sieve belongs to a typical microporous material, and has problems of low mass transfer efficiency and poor accessibility of active sites. In order to overcome these limitations, mesopores (2-50 nm) can be introduced into the microporous crystal to prepare a hierarchical pore molecular sieve. The hierarchical pore molecular sieve can make the reactants effectively contact with the active sites and react, and the generated products can quickly diffuse from the pores to avoid the occurrence of secondary reactions, thereby accelerating the reaction rate and prolonging the catalyst life. On the other hand, the mesopores or macropores of the hierarchical pore molecular sieve create an ideal space for the deposition of the catalytically active phase, so that the catalytically active phase is highly dispersed in the molecular sieve and strong interaction occurs. Therefore, it is of great significance to develop a hierarchical pore LSX molecular sieve.

[0003] The published document (Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2008, 318(1): 269-274.) reports that a hierarchical pore X-type molecular sieve is synthesized using polydiallyldimethylammonium chloride (PDADMAC) and spirulina (SP) as mesopore template agents. The synthesized X-type molecular sieve is characterized by transmission electron microscopy, and the results show that there are mesopores with a size of 4-50 nm, and its calcium ion exchange capacity is higher than that of the conventional microporous X-type molecular sieve, which is of great significance for the industrial application of the X-type molecular sieve as a high-efficiency adsorbent and ion exchanger.

[0004] The published document (Angewandte Chemie International Edition, 2012, 51(8): 1962-1965.) reports that a hierarchical pore X-type molecular sieve with intracrystalline mesopores with a size of 7 nm is synthesized using hexadecyltrimethoxysilane organosilicon chloride ammonium. This material can overcome the problem of limited diffusion of macromolecules when used as an adsorbent or catalyst. The published document (Catalysis Communications, 2016, 78: 55-58.) reports that sodium dodecylbenzenesulfonate is used as a template agent to synthesize a hierarchical pore X-type molecular sieve. The innovation of this research lies in the use of an anionic surfactant as a template agent. The synthesized hierarchical pore X-type molecular sieve as a catalyst enhances the deoxy ability of m-benzoic acid, improves the toluene yield, and reduces the deactivation rate of the catalyst.

[0005] The disclosed document (Chemical Engineering Journal, 2017, 308:476-491.) reports that using a hard template method, inorganic chemical reagents are used as raw materials to synthesize silico-aluminosilicate gels, and porous carriers (diatomite and carbon) are added to synthesize hierarchical pore X molecular sieve-diatomite and hierarchical pore X molecular sieve-carbon composite materials by a hydrothermal method. The composite material is used as an adsorbent to remove Mn 2+ Compared with conventional microporous X molecular sieves, the hierarchical pore X molecular sieves have higher ion exchange capacity.

[0006] In summary, the preparation of hierarchical pore X molecular sieves by the template method has achieved remarkable success, but the mesoporous / macroporous template used in the above method is expensive and needs to be removed from the molecular sieve structure by high-temperature calcination. The high-temperature calcination process causes the destruction of the template structure, cannot be recycled, and emits a large amount of carbon dioxide, nitrogen oxides and toxic halogens that are harmful to the environment. Therefore, it is necessary and urgent to develop an efficient, recyclable and environmentally friendly mesoporous template and use it to synthesize hierarchical pore X molecular sieves. SUMMARY

[0007] Therefore, it is necessary to provide a polymer template, hierarchical pore LSX molecular sieve and a green preparation method thereof to solve the problems of structural damage caused by high-temperature calcination for removing mesoporous or macroporous templates in the prior art, and the inability to be recycled repeatedly, as well as the high production cost and environmental pollution of producing hierarchical pore X molecular sieves.

[0008] To achieve the above-mentioned purpose, in a first aspect, the present application provides a polymer template, the number average molecular weight of which is 26000-32000 g / mol, and the chemical structural formula of which is as follows:

[0009]

[0010] wherein n is an integer greater than 1.

[0011] In a second aspect, the present application provides a preparation method of the polymer template according to the first aspect of the present application, comprising the following steps:

[0012] Isopropyl acrylamide and azobisisobutyronitrile are added to a polymerization tube containing anhydrous tetrahydrofuran, and the reaction is carried out in an oil bath under the protection of nitrogen. After cooling, the solvent is evaporated, dissolved in acetone, and then dropped into n-hexane drop by drop. After filtration and vacuum drying, poly-N-isopropyl acrylamide is obtained.

[0013] The poly-N-isopropyl acrylamide is dissolved in diethyl ether, and bromoethane is added. After reaction, a brown solid is obtained.

[0014] The brown solid is recrystallized with ethanol to generate a white solid, and then the white solid is filtered by adding acetone to obtain the polymer template agent.

[0015] As a preferred embodiment of the present application, the molar ratio of isopropyl acrylamide, azobisisobutyronitrile and anhydrous tetrahydrofuran is (6-10):(0.02-0.06):(60-150).

[0016] As a preferred embodiment of the present application, the temperature of the oil bath reaction is 60-80℃, the time of the oil bath reaction is 24-36h, the temperature of the vacuum drying is 25-35℃, and the time of the vacuum drying is 24-48h.

[0017] As a preferred embodiment of the present application, the dosage of bromoethane is 100-180mmol, the reaction temperature is 40-50℃, and the reaction time is 18-36h.

[0018] In a third aspect, the present application provides a green preparation method of the hierarchical pore LSX molecular sieve, comprising the following steps:

[0019] The water, the aluminum source, the alkali source, sodium chloride and the polymer template agent of the first aspect of the present application are uniformly mixed, and the silicon source is added in batches to obtain a gel, so that the molar fraction ratio of H2O, SiO2, Al2O3, Na2O, K2O and the polymer template agent in the gel is (122-180):(2-4):1:(2.6-4):(0.12-0.2):(0.002-0.008);

[0020] The gel is aged and then placed in a reaction kettle to perform a crystallization reaction to obtain a crystallization product;

[0021] The crystallization product is centrifuged and dried to obtain the hierarchical pore LSX molecular sieve.

[0022] The inventors accidentally found that when the polymer template agent is used, the components in the gel within the above range can prepare the hierarchical pore LSX molecular sieve. Otherwise, the molecular sieve pore size may be too small to tend to small micropores, and the hierarchical pore LSX molecular sieve cannot be obtained.

[0023] In addition, the inventors also found that not all kinds of silicon and aluminum sources can be used in the preparation process of the molecular sieve. After a large number of experimental explorations, the present application selects some raw materials that can prepare the LSX molecular sieve.

[0024] As a preferred embodiment of the present application, the aluminum source is selected from one or any two or more of sodium metaaluminate, aluminum sulfate and aluminum isopropoxide.

[0025] As a preferred embodiment of the present application, the silicon source is selected from one or more than two of silica sol, industrial silica gel, white carbon black, and water glass.

[0026] The centrifugal parameter of the crystallization product of the present application is determined in consideration of the requirements of removing the polymer template and saving energy. As a preferred embodiment of the present application, the rotation speed is 5500-8500 rpm, the treatment temperature is 20-35℃, and the treatment time is 8-20 min when the crystallization product is centrifuged.

[0027] In a fourth aspect, the present application provides a hierarchical-pore LSX molecular sieve prepared by the green preparation method of the third aspect of the present application. The mesopore size of the hierarchical-pore LSX molecular sieve is concentrated at 20-50 nm, the specific surface area is 730-890 m 2 / g, and the pore volume is 0.55-0.65 cm 3 / g.

[0028] Differing from the prior art, the above technical solution uses a polymer template with a special chemical structure, so that the synthesized LSX molecular sieve contains both micropores and mesopores, forming a hierarchical-pore structure, effectively solving the problems of low mass transfer efficiency and poor accessibility of active sites caused by the microporous structure of conventional LSX molecular sieves. At the same time, the polymer template provided by the present application can be fully removed by centrifugation, without the need for high-temperature calcination of the synthesized LSX molecular sieve, not only saving energy, but also avoiding environmental pollution caused by high-temperature calcination. Moreover, the hierarchical-pore LSX molecular sieve prepared by using the polymer template provided by the present application has a mesopore size concentrated at 20-50 nm, a specific surface area of 700-820 m 2 / g, and a pore volume of 0.55-0.65 cm 3 / g, which greatly improves the performance of the LSX molecular sieve. In addition, since the polymer template provided by the present application can be removed by centrifugation and recycled for the preparation of hierarchical-pore LSX molecular sieves, the production cost of the hierarchical-pore LSX molecular sieve is greatly reduced, which is worthy of industrial popularization and application. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 is the XRD diffraction pattern of the hierarchical-pore LSX molecular sieve prepared in Example 1 of the present application;

[0030] Figure 2 is the FIB-SEM photo of the hierarchical-pore LSX molecular sieve prepared in Example 1 of the present application;

[0031] Figure 3 is the XRD diffraction pattern of the product prepared in Comparative Example 1 of the present application;

[0032] Figure 4is the XRD diffraction pattern of the product prepared in Inventive Example 2.

[0033] Figure 5 is the XRD diffraction pattern of the product prepared in Inventive Example 3. DETAILED DESCRIPTION

[0034] To clearly illustrate the technical content, structural features, and purposes and effects of the technical solutions, the following will be described in detail with specific embodiments and in conjunction with the drawings.

[0035] Reference to "embodiments" in this document means that the specific features, structures, or characteristics described in connection with the embodiments can be included in at least one embodiment of the present application. The word "embodiments" appearing in various places in the specification does not necessarily refer to the same embodiment, nor does it particularly limit the independence or association between other embodiments. In principle, in the present application, as long as there is no technical contradiction or conflict, each technical feature mentioned in each embodiment can be combined in any way to form a corresponding implementable technical solution.

[0036] Unless otherwise defined, the meanings of the technical terms used in the present application are the same as those commonly understood by those skilled in the art to which the present application belongs; the use of related terms in the present application is only for the purpose of describing specific embodiments, and is not intended to limit the present application.

[0037] In the description of the present application, the word "and / or" is a description of the logical relationship between the objects, which means that there can be three relationships, for example, A and / or B, which means that there are three cases: A exists, B exists, and A and B exist at the same time. In addition, the character " / " in the present application generally represents that the associated objects before and after are a "or" logical relationship.

[0038] In the present application, such as "first" and "second", the words are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual quantity, primary and secondary or order relationship between the entities or operations.

[0039] In the present application, without more limitations, the words "include", "contain", "have" or other similar expressions used in the sentence are intended to cover non-exclusive inclusion, and these expressions do not exclude the presence of other elements in the process, method or product including the described elements, so that the process, method or product including a series of elements can not only include those limited elements, but also include other elements not explicitly listed, or also include the elements inherent to such process, method or product.

[0040] As the same as the understanding in the "Examination Guidelines", in the present application, "greater than", "less than", "exceed" and the like are understood as not including the number; "above", "below", "within" and the like are understood as including the number. In addition, in the description of the embodiments of the present application, the meaning of "multiple" is two or more (including two), and similar expressions related to "multiple" are also understood in this way, for example, "multiple groups", "multiple times" and the like, unless otherwise explicitly and specifically limited.

[0041] In the description of the embodiments of the present application, the spatially-related expressions used, such as "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "perpendicular", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", and the like, indicate the orientation or positional relationship based on the orientation or positional relationship shown in the specific embodiments or the drawings, and are only for the convenience of describing the specific embodiments of the present application or for the reader to understand, and do not indicate or imply that the indicated device or component must have a specific position, a specific orientation, or be constructed or operated in a specific orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0042] Unless otherwise explicitly specified or limited, in the description of the embodiments of the present application, the terms "mount", "connect", "connect", "fix", "set", and the like should be understood broadly. For example, the "connection" can be a fixed connection, or a detachable connection, or an integral setting; it can be a mechanical connection, or an electrical connection, or a communication connection; it can be directly connected, or indirectly connected through an intermediate medium; it can be the communication or interaction relationship between two elements. For those skilled in the art to which the present application belongs, the specific meaning of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0043] The hierarchical-pore LSX molecular sieve is usually prepared by the following process: first, hydrothermal crystallization reaction is carried out at high temperature (80-110°C) with organic amine, inorganic amine or alcohol as a template agent, the temperature is lowered to room temperature after the crystallization reaction to obtain the molecular sieve, and then calcination is carried out at a certain temperature to remove the template to obtain the hierarchical-pore LSX molecular sieve. The above-mentioned template agent generally has the problems of high cost, structure damage caused by high-temperature calcination for removal, non-recyclable and emission of harmful substances. Based on this, the inventors have unexpectedly developed a polymer which can also be used as a template agent and applied to the synthesis of the hierarchical-pore LSX molecular sieve. At the same time, this template agent can be removed by centrifugation at room temperature and can be recycled, effectively reducing the manufacturing cost and energy consumption of the hierarchical-pore LSX molecular sieve, and the effect of solving the above problems is very remarkable.

[0044] In the present application, unless otherwise specified, the reagents and raw materials used are commercially available.

[0045] In the present application, unless otherwise specified, the number average molecular weight of the polymer template is measured by gel chromatography, and the specific test conditions and methods are as follows:

[0046] The test is performed by using a liquid chromatograph (Japan Shimadzu) with a model LC-10AD / SPD-10A and a gel chromatographic column (Japan Shimadzu) with a model Shodex KF-803, 4 mg of the polymer template is dissolved in 2 mL of tetrahydrofuran solution, filtered by a 2 μm filter, and then 20 μL of the above sample is taken for testing the molecular weight distribution of the polymer template in the liquid chromatograph, the test temperature is 30°C, the chromatographically pure TCM is used as the solvent, the solvent flow rate is 1 mL / min, and polystyrene is used as the standard sample.

[0047] In the present application, unless otherwise specified, the mesopore size of the hierarchical pore LSX molecular sieve is measured by physical adsorption, and the specific test conditions and methods are as follows:

[0048] The test is performed by using a physical adsorption instrument (USA Micromeritics) with a model Micromeritics 2020, the sample is pretreated by vacuum at 150°C for 12 h, then static adsorption is performed at -196°C by using Ar as the adsorbate, the adsorption-desorption curve of the sample is determined, and the Barrett-Joyner-Halenda (BJH) model is used to obtain the mesopore size distribution of the sample.

[0049] In the present application, unless otherwise specified, the specific surface area of the hierarchical pore LSX molecular sieve is measured by physical adsorption, and the specific test conditions and methods are as follows:

[0050] The test is performed by using a physical adsorption instrument (USA Micromeritics) with a model Micromeritics 2020, the sample is pretreated by vacuum at 150°C for 12 h, then static adsorption is performed at -196°C by using Ar as the adsorbate, the adsorption-desorption curve of the sample is determined, and the Barrett-Joyner-Halenda (BJH) model is used to obtain the mesopore size distribution of the sample. 0 <0.30) part of the adsorption isotherm is used to calculate the total specific surface area by using the BET equation; the micropore and mesopore specific surface areas are calculated by using the t-plot method.

[0051] In the present application, unless otherwise specified, the pore volume of the hierarchical pore LSX molecular sieve is measured by physical adsorption, and the specific test conditions and methods are as follows:

[0052] The physical adsorption instrument (Micromeritics 2020, USA) was used for testing. Before testing, the sample was vacuum pretreated at 150 DEG C for 12 hours, and then Ar was used as the adsorbate to perform static adsorption at -196 DEG C to determine the adsorption-desorption curve of the sample. The micropore and mesopore volumes were calculated by the t-plot method.

[0053] In the present application, unless otherwise specified, the crystallinity was measured by X-ray diffraction (XRD) method, and the specific test conditions were as follows:

[0054] The X-ray diffractometer (Rigaku D-Max 2550, Japan) was used to analyze the phase structure of the synthesized molecular sieve sample, and the test conditions were as follows: Cu target, Kα ray tube voltage 40 kV, tube current 40 mA. The wide-angle scanning range was 2 theta = 5-50 DEG, and the scanning rate was 7 DEG / min. The relative crystallinity described in the embodiments of the present application was determined according to the standard of ASTM D3906-03 (2013), and the ratio of the sum of the integral areas of 2 theta at 15.7 DEG ± 0.2 DEG, 18.7 DEG ± 0.2 DEG, 20.4 DEG ± 0.3 DEG, 23.7 DEG ± 0.4 DEG, 27.1 DEG ± 0.5 DEG, 30.8 DEG ± 0.5 DEG, 31.5 DEG ± 0.5 DEG, and 34.2 DEG ± 0.5 DEG in the XRD spectrum of the obtained product and the LSX molecular sieve standard sample, and the standard sample was the LSX molecular sieve with a silicon-aluminum ratio of 2.33 produced by the Catalyst Factory of Nankai University. The crystallinity was defined as 100%.

[0055] In the present application, unless otherwise specified, the SiO2 / Al2O3 was measured by ICP method, and the specific test conditions were as follows:

[0056] The OPTIMA 8000 type inductively coupled plasma emission spectrometer produced by the Perkin-Elmer Company of the United States was used. First, 10 mg of the sample was dissolved in aqua regia solution, transferred to a microwave digestion instrument, heated to 200 DEG C and kept for 2 hours to completely dissolve it; then cooled to room temperature and constant volume was performed with a volumetric flask; then the standard liquid of the metal element to be tested was prepared as a reference standard to draw a standard curve; then argon was used as the carrier gas to test the sample to be tested; finally, the concentration of the metal element to be tested was obtained and recorded.

[0057] In the present application, unless otherwise specified, the FIB-SEM was used to characterize the cross-sectional morphology of the molecular sieve, and the specific test conditions were as follows:

[0058] FIB-SEM was performed on a Helios G4 CX focused ion beam (FIB) dual beam field emission scanning electron microscope (Thermo Scientific, USA), in which the FIB was used for cross-sectional microstructure observation of the synthesized molecular sieve. A small amount of dried sample was dispersed in an ethanol solution, ultrasonically treated for 10 min to uniformly disperse, and then one drop of the upper liquid was dropped on a clean silicon wafer, which was placed in a 60°C oven for 10 min, followed by gold spraying. During the test, the ion beam was used for cutting, and finally the electron microscope image was obtained and the picture was analyzed.

[0059] Example 1

[0060] Polymer template and preparation method thereof

[0061] 6 mmol of isopropyl acrylamide and 0.02 mmol of azobisisobutyronitrile were added to a polymerization tube containing 60 mmol of anhydrous tetrahydrofuran, and the reaction was carried out at 60°C for 24 h under oil bath and nitrogen protection. After cooling to room temperature, the solvent was evaporated, a small amount of acetone was used for dissolution, and then it was dropped into n-hexane drop by drop. After filtration, vacuum drying was carried out at 30°C for 48 h to obtain white solid of poly-N-isopropyl acrylamide. The above white solid was dissolved in diethyl ether, 100 mmol of bromoethane was added, and the reaction was carried out at 45°C for 24 h to obtain brown solid. White solid was generated after recrystallization with ethanol, and acetone was added for rapid filtration to obtain the product PJN shown in the chemical structural formula I. The number average molecular weight of the product was detected to be 26500 g / mol.

[0062]

[0063] Example 2

[0064] Polymer template and preparation method thereof

[0065] 9 mmol of isopropyl acrylamide and 0.05 mmol of azobisisobutyronitrile were added to a polymerization tube containing 100 mmol of anhydrous tetrahydrofuran, and the reaction was carried out at 75°C for 32 h under oil bath and nitrogen protection. After cooling to room temperature, the solvent was evaporated, a small amount of acetone was used for dissolution, and then it was dropped into n-hexane drop by drop. After filtration, vacuum drying was carried out at 35°C for 24 h to obtain white solid of poly-N-isopropyl acrylamide. The above white solid was dissolved in diethyl ether, 150 mmol of bromoethane was added, and the reaction was carried out at 45°C for 30 h to obtain brown solid. White solid was generated after recrystallization with ethanol, and acetone was added for rapid filtration to obtain the product PJN shown in the chemical structural formula I. The number average molecular weight of the product was detected to be 29600 g / mol.

[0066] Example 3

[0067] Polymer template and preparation method thereof

[0068] Into a polymerization tube, 10 mmol of isopropyl acrylamide and 0.06 mmol of azobisisobutyronitrile were added into 150 mmol of anhydrous tetrahydrofuran, and the mixture was reacted at 80°C for 30 hours under oil bath in a nitrogen environment. After cooling to room temperature, the solvent was evaporated, and the residue was dissolved in a small amount of acetone, and then dropped into n-hexane drop by drop. After suction filtration, the product was dried at 25°C under vacuum for 48 hours to obtain white solid of poly-N-isopropyl acrylamide. The white solid was dissolved in diethyl ether, and 180 mmol of bromoethane was added. The mixture was reacted at 45°C for 32 hours to obtain brown solid. White solid was obtained after recrystallization from ethanol. The product PJN as shown in Chemical Structural Formula I was obtained after rapid filtration with acetone. The number average molecular weight of the product was 30,500 g / mol.

[0069] Example 4

[0070] Polymer template and method for preparing the same

[0071] Into a polymerization tube, 10 mmol of isopropyl acrylamide and 0.06 mmol of azobisisobutyronitrile were added into 150 mmol of anhydrous tetrahydrofuran, and the mixture was reacted at 80°C for 30 hours under oil bath in a nitrogen environment. After cooling to room temperature, the solvent was evaporated, and the residue was dissolved in a small amount of acetone, and then dropped into n-hexane drop by drop. After suction filtration, the product was dried at 25°C under vacuum for 48 hours to obtain white solid of poly-N-isopropyl acrylamide. The white solid was dissolved in diethyl ether, and 180 mmol of bromoethane was added. The mixture was reacted at 45°C for 32 hours to obtain brown solid. White solid was obtained after recrystallization from ethanol. The product PJN as shown in Chemical Structural Formula I was obtained after rapid filtration with acetone. The number average molecular weight of the product was 30,500 g / mol.

[0072] Example 5

[0073] A stepped-pore LSX molecular sieve was prepared by the following steps using the polymer template provided in Example 1 by a hydrothermal method:

[0074] Hydrothermal synthesis of molecular sieve: 0.782 g of NaOH and 0.5 g of KOH were dissolved in 27.39 mL of deionized water, after continuous stirring for 10 min, 2.5 g of sodium aluminate and 4.2 g of sodium chloride were added, and stirring was continued for 10 min, 0.81 g of polymer template agent PJN provided in Example 1 was added, and finally 1.87 g of white carbon black was added, so that the composition of the synthesis gel was 2SiO2 / 1Al2O3 / 4Na2O / 0.2K2O / 122H2O / 0.002 polymer template agent PJN, and the obtained gel was aged at 25°C for 6 h, and then transferred into a 50 mL stainless steel autoclave with a polytetrafluoroethylene liner, and crystallized at 80°C for 8 h to obtain sample A. The polymer template agent PJN locks the molecular sieve precursor inside the gel at the synthesis temperature of LSX molecular sieve, and guides the formation of the crystal structure of LSX molecular sieve, and after crystallization, the shell of the polymer template agent PJN opens, and the molecular sieve crystals locked inside are released by diffusion, and the polymer template agent PJN can be separated from the molecular sieve by centrifugation.

[0075] The sample A was centrifuged to remove the template agent, and at the same time, the hierarchical LSX molecular sieve was obtained. The sample was centrifuged at a speed of 6500 rpm and a temperature of 25°C for 10 min, and the upper layer was the polymer template agent PJN, and the lower layer was a solid. The solid was washed with deionized water until the pH was about 7, and then dried at 105°C for 12 h to obtain sample B. The XRD diffraction pattern of the sample B is shown in Figure 1 , and the phase of the obtained solid powder belongs to LSX molecular sieve, and the relative crystallinity is 97%, and the SiO2 / Al2O3 ratio measured by ICP is 2.

[0076] Please refer to the FIB-SEM characterization figure of Figure 2 , Figure 2 , which shows that the sample B has a through mesoporous structure inside, and therefore, the sample B is a hierarchical LSX molecular sieve containing microporous and mesoporous structures.

[0077] The Ar adsorption and desorption test was carried out using the sample B, and the results are shown in Table 1. According to the Ar adsorption and desorption results, the mesopore size of the sample B is concentrated at 30 nm, the specific surface area is 751 m 2 / g, the pore volume is 0.58 cm 3 / g, wherein the micropore volume is 0.32 cm 3 / g, and the mesopore volume is 0.26 cm 3 / g.

[0078] Table 1: Textural parameters of hierarchical LSX molecular sieve

[0079]

[0080] Example 6

[0081] A hierarchical-pore LSX molecular sieve and a preparation method thereof (using a centrifugally recovered polymer template as a template)

[0082] The method of Example 5 was followed, except that the polymer template PJN obtained by centrifugal removal in Example 5 was used as the template. The phase of the product obtained in this example was determined by XRD to be LSX molecular sieve, the relative crystallinity was 96%, SiO2 / Al2O3 was 2, the mesopore size was concentrated at 30 nm, the specific surface area was 742 m 2 / g, the pore volume was 0.55 cm 3 / g, wherein the micropore volume was 0.31 cm 3 / g, the mesopore volume was 0.24 cm 3 / g.

[0083] The XRD diffraction pattern of the hierarchical-pore LSX molecular sieve of this example was similar to that of Figure 1 The FIB-SEM characterization pattern of the hierarchical-pore LSX molecular sieve was similar to that of Figure 2 .

[0084] Example 7

[0085] A hierarchical-pore LSX molecular sieve and a preparation method thereof

[0086] A hierarchical-pore LSX molecular sieve was prepared by a hydrothermal method using a recoverable polymer template as a template by the following steps:

[0087] Preparation of the molecular sieve by a hydrothermal method: the polymer template PJN prepared in Example 2 was used, aluminum sulfate was used as the aluminum source, and sol and white carbon black were used as the silicon source, the order of addition of raw materials was the same as in Example 5, and the addition amount was adjusted to satisfy the molar ratio of the feed: 3SiO2 / 1Al2O3 / 3.5Na2O / 0.16K2O / 150H2O / 0.003 polymer template PJN, the obtained gel was aged at 25°C for 10 h, and then transferred to a 50 mL stainless steel autoclave with a polytetrafluoroethylene liner, and crystallized at 90°C for 7 h to obtain sample A.

[0088] The template was removed from sample A by centrifugation to obtain a hierarchical-pore LSX molecular sieve. The centrifugation rate of sample A was 7500 rpm, the treatment temperature was 25°C, and the centrifugation time was 15 min, the upper solid obtained was the polymer template PJN, and the lower solid was obtained; the above solid was washed with deionized water until the pH was about 7, and then dried at 105°C for 12 h to obtain a solid powder. The XRD diffraction pattern of the obtained solid powder was similar to that of Figure 1 , the phase was LSX molecular sieve, the relative crystallinity was 98%, SiO2 / Al2O3 was 2.10, the mesopore size was concentrated at 50 nm, and the specific surface area was 789 m2 / g, the micropore volume is 0.32 cm 3 / g, the micropore volume is 0.32 cm 3 / g, the mesopore volume is 0.27 cm 3 / g.

[0089] Example 8

[0090] A hierarchical LSX molecular sieve was prepared by a hydrothermal method using a recoverable polymer template as a template by the following steps:

[0091] Preparation of a molecular sieve by a hydrothermal method: the polymer template PJN prepared in Example 3 was used, aluminum isopropoxide was used as an aluminum source, and water glass was used as a silicon source. The raw materials were added in the same order as in Example 5, and the addition amount was adjusted so that the molar ratio of the feed met: the composition of the synthesis gel was 4SiO2 / 1Al2O3 / 2.6Na2O / 0.12K2O / 180H2O / 0.005 polymer template PJN, and the obtained gel was aged at 25°C for 12h. The gel was transferred to a 50mL stainless steel autoclave with a polytetrafluoroethylene liner, and crystallization was carried out at 100°C for 10h to obtain sample A.

[0092] The template was removed by centrifugation of sample A, and a hierarchical LSX molecular sieve was obtained. The centrifugation rate of sample A was 8500rpm, the treatment temperature was 25°C, and centrifugation was carried out for 15min to obtain PJN in the upper layer and a solid in the lower layer; the solid was washed with deionized water until the pH was about 7, and then dried at 105°C for 12h to obtain a solid powder. The obtained solid powder was determined by XRD, and the XRD diffraction pattern was similar to that of a LSX molecular sieve, the relative crystallinity was 96%, the SiO2 / Al2O3 was 2.2, the mesopore size was concentrated at 40nm, and the specific surface area was 800m Figure 1 / g, the micropore volume is 0.32 cm 2 / g, the micropore volume is 0.32 cm 3 / g, the micropore volume is 0.32 cm 3 / g, the mesopore volume is 0.29 cm 3 / g.

[0093] Comparative Example 1

[0094] A molecular sieve and a preparation method thereof

[0095] The polymer template PJN prepared in the present application was not added, and the other operations were the same as in Example 5. The phase of the obtained product was determined by XRD to be a NaA molecular sieve (for details, see Figure 3 ).

[0096] Comparative Example 2

[0097] A kind of molecular sieve and its preparation method do not add the polymer template agent PJN prepared in the application, other same with example 7.XRD determination shows that the phase of the obtained product belongs to the mixture of NaA molecular sieve and NaX molecular sieve (for details, please refer to Figure 4 ).

[0098] Comparative example 3

[0099] A kind of molecular sieve and its preparation method

[0100] Without adding the polymer template agent PJN prepared in the application, other operation steps are same with example 8.XRD determination shows that the phase of the obtained product is amorphous (for details, please refer to Figure 5 ).

[0101] From the comparison results of above-mentioned examples 5-8 and comparative examples 1-3, it can be seen that the LSX molecular sieve synthesized by the method of the application contains micropore and mesopore in structure, which is a hierarchical pore structure, effectively solving the mass transfer problem caused by traditional LSX microporous molecular sieve.The phase of the molecular sieve synthesized by the method of comparative examples 1-3 does not belong to LSX molecular sieve, so there is no basis to further discuss whether the LSX molecular sieve with micropore-mesopore hierarchical pore diameter is formed inside the molecular sieve, that is, the polymer template agent provided by the application cannot be used in comparative examples 1-3 to solve the technical problems of the application.

[0102] And, as the amount of polymer template agent increases within a proper range, the pore size also increases, as can be seen from the mesopore size distribution of the hierarchical pore diameter LSX molecular sieve obtained by examples 5-8.

[0103] Meanwhile, the polymer template agent PJN used in the method of the application can be removed only by centrifugation, and can be recycled, reducing the cost and improving the atomic utilization rate.Furthermore, the LSX molecular sieve synthesized therefrom does not need high-temperature calcination, and has the advantages of high efficiency, green and environmental protection.

[0104] In addition, compared with conventional molecular sieves, the LSX molecular sieve synthesized by the method of the application has a higher specific surface area of 730-890 m 2 / g and a pore volume of 0.55-0.65 cm 3 / g, and the application performance of the LSX molecular sieve is better and more excellent, thereby expanding the application range.

[0105] It should be noted that although the above examples have been described in this paper, the patent protection scope of the application is not limited thereby. Therefore, based on the innovative idea of the application, the changes and modifications of the examples described in this paper, or the equivalent structure or equivalent process transformation made by using the content of the application specification and drawings, directly or indirectly apply the above technical solutions to other related technical fields, are all included in the patent protection scope of the application.

Claims

1. A polymeric templating agent, characterized in that, The number average molecular weight is 26000-32000 g / mol, and the chemical structural formula is shown as follows: Wherein, n is an integer greater than 1.

2. A method for preparing the polymeric templating agent of claim 1, characterized in that, The method comprises the following steps: Isopropyl acrylamide and azobisisobutyronitrile are added into a polymerization tube containing anhydrous tetrahydrofuran, and oil bath reaction is carried out under a nitrogen protection environment, and then cooling, evaporation, dissolution in acetone, dropwise addition into n-hexane, suction filtration and vacuum drying are carried out to obtain poly-N-isopropyl acrylamide; The poly-N-isopropyl acrylamide is dissolved in diethyl ether, and bromoethane is added to obtain a brown solid after reaction; The brown solid is recrystallized with ethanol, and acetone is added for filtration to obtain the polymer template.

3. The preparation method according to claim 2, characterized in that, The molar amount of isopropyl acrylamide, azobisisobutyronitrile and anhydrous tetrahydrofuran is (6-10):(0.02-0.06):(60-150).

4. The production method according to claim 2, characterized by, The oil bath reaction temperature is 60-80℃, the oil bath reaction time is 24-36h, the vacuum drying temperature is 25-35℃, and the vacuum drying time is 24-48h.

5. The preparation method according to claim 2, characterized in that, The amount of bromoethane is 100-180mmol, the reaction temperature is 40-50℃, and the reaction time is 18-36h.

6. A green process for the preparation of a stepped-pore LSX molecular sieve, characterized in that, The method comprises the following steps: The water, aluminum source, alkali source, sodium chloride and the polymer template of claim 1 are uniformly mixed, and the silicon source is added in batches to obtain a gel, so that the molar fraction ratio of H2O, SiO2, Al2O3, Na2O, K2O and the polymer template in the gel is (122-180):(2-4):1:(2.6-4):(0.12-0.2):(0.002-0.008); The gel is aged and then placed in a reaction kettle for crystallization reaction to obtain a crystallization product; The crystallization product is centrifuged and dried to obtain the hierarchical pore LSX molecular sieve.

7. The green manufacturing method of claim 6, wherein, The aluminum source is selected from one or any two or more of sodium metaaluminate, aluminum sulfate and aluminum isopropyl alcohol.

8. The green manufacturing method of claim 6, wherein, The silicon source is selected from one or any two or more of silica sol, industrial silica gel, white carbon black and water glass.

9. The green manufacturing method of claim 6, wherein, When the crystallization product is centrifuged, the rotation speed is 5500-8500rpm, the treatment temperature is 20-35℃, and the treatment time is 8-20min.

10. The stepped-pore LSX molecular sieve prepared by the green preparation method of any one of claims 6-9, characterized in that, The mesopore size of the hierarchical-pore LSX molecular sieve is concentrated at 20-50 nm, the specific surface area is 730-890 m 2 / g, and the pore volume is 0.55-0.65 cm 3 / g.

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